Wideband Planar Array Antenna Based on SCRLH-TL for Airborne Synthetic Aperture Radar Application

This paper presents empirical results of a novel planar microstrip array antenna based on a simplified composite right/left-handed transmission-line (SCRLH-TL) for application in circularly polarized synthetic aperture radar (CP-SAR) systems operated in UHF, L, S and C-Bands. The array antenna consists of 6×6 matrix of spiral shaped radiating elements that are excited through proximity-coupled, single feed-line. Pattern synthesis technique is used to determine the excitation coefficients (amplitude and phase) to apply to the individual array elements to achieve the required pattern shape. The array antenna has dimensions of 111.5×96.06 mm2. The measured impedance bandwidth of the antenna is 3.85 GHz for S11 < -10 dB from 300 MHz to 4.15 GHz, corresponding to a fractional bandwidth of 173%. Maximum gain and radiation efficiency measured are 4.8 dBi and 79.5%, respectively, at 2.40 GHz. The antenna has a 3-dB axial-ratio bandwidth of 3.94 GHz from 144 MHz to 4.66 GHz. The antenna’s beamwidth in azimuth and elevation planes vary between 60° and 120° across its operational frequency range from 300 MHz to 4.15 GHz. The antenna design fulfills the challenging electrical and physical specifications required for CP-SAR employed onboard unmanned aerial vehicle (UAV)

Radar Sub-surface Sensing for Mapping the Extent of Hydraulic Fractures and for Monitoring Lake Ice and Design of Some Novel Antennas.

Hydraulic fracturing, which is a fast-developing well-stimulation technique, has greatly expanded oil and natural gas production in the United States. As the use of hydraulic fracturing has grown, concerns about its environmental impacts have also increased. A sub-surface imaging radar that can detect the extent of hydraulic fractures is highly demanded, but existing radar designs cannot meet the requirement of penetration range on the order of kilometers due to the exorbitant propagation loss in the ground. In the thesis, a medium frequency (MF) band sub-surface radar sensing system is proposed to extend the detectable range to kilometers in rock layers. Algorithms for cross-hole and single-hole configurations are developed based on simulations using point targets and realistic fractured rock models. A super-miniaturized borehole antenna and its feeding network are also designed for this radar system. Also application of imaging radars for sub-surface sensing frozen lakes at Arctic regions is investigated. The scattering mechanism is the key point to understand the radar data and to extract useful information. To explore this topic, a full-wave simulation model to analyze lake ice scattering phenomenology that includes columnar air bubbles is presented. Based on this model, the scattering mechanism from the rough ice/water interface and columnar air bubbles in the ice at C band is addressed and concludes that the roughness at the interface between ice and water is the dominate contributor to backscatter and once the lake is completely frozen the backscatter diminishes significantly. Radar remote sensing systems often require high-performance antennas with special specifications. Besides the borehole antenna for MF band subsurface imaging system, several other antennas are also designed for potential radar systems. Surface-to-borehole setup is an alternative configuration for subsurface imaging system, which requires a miniaturized planar antenna placed on the surface. Such antenna is developed with using artificial electromagnetic materials for size reduction. Furthermore, circularly polarized (CP) waveform can be used for imaging system and omnidirectional CP antenna is needed. Thus, a low-profile planar azimuthal omnidirectional CP antenna with gain of 1dB and bandwidth of 40MHz is designed at 2.4GHz by combining a novel slot antenna and a PIFA antenna.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120674/1/wujf_1.pd

Sequential 90° Rotation of Dual-Polarized Antenna Elements in Linear Phased Arrays with Improved Cross-Polarization Level for Airborne Synthetic Aperture Radar Applications

[EN] In this work, a novel rotation approach for the antenna elements of a linear phased array is presented. The proposed method improves by up to 14 dB the cross-polarization level within the main beam by performing a sequential 90° rotation of the identical array elements, and achieving measured cross-polarization suppressions of 40 dB. This configuration is validated by means of simulation and measurements of a manufactured linear array of five dual-polarized cavity-box aperture coupled stacked patch antennas operating in L-Band, and considering both uniform amplitude and phase distribution and beamforming with amplitude tapering. The analysis is further extended by applying and comparing the proposed design with the 180° rotation and non-rotation topologies. This technique is expected to be used for the next generation L-Band Airborne Synthetic Aperture Radar Sensor of the German Aerospace Center (DLR).Lorente-Catalán, D.; Limbach, M.; Gabler, B.; Esteban González, H.; Boria Esbert, VE. (2021). Sequential 90° Rotation of Dual-Polarized Antenna Elements in Linear Phased Arrays with Improved Cross-Polarization Level for Airborne Synthetic Aperture Radar Applications. Remote Sensing. 13(8). https://doi.org/10.3390/rs1308143013

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Design of a Wearable, Low-Cost, Through-Wall Doppler Radar System

A novel, low-cost, low-weight, wearable Doppler radar system composed of textile materials and capable of detecting moving objects behind a barrier is presented. The system operates at 2.35 GHz and is integrable into garments, making it well-suited for usage in difficult to access terrain, such as disaster areas or burning buildings. Wearability is maximized by relying on flexible, low-weight, and breathable materials to manufacture the key parts of the system. The low-complexity Doppler radar system makes use of an array of four textile-transmit antennas to scan the surroundings. The beam emitted by this array is right-hand circularly polarized along all scanning angles and provides a measured gain of 9.2 dBi. At the receiving end, textile materials are used to develop an active wearable receive antenna, with 15.7 dBi gain, 1.1 dB noise figure, left-hand circular polarization, and a 3 dB axial ratio beamwidth larger than 50°. Several measurement setups demonstrate that the onbody system is capable of detecting multiple moving subjects in indoor environments, including through-wall scenarios

2009 Index IEEE Antennas and Wireless Propagation Letters Vol. 8

This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author\u27s name. The primary entry includes the coauthors\u27 names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author\u27s name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index

2008 Index IEEE Transactions on Control Systems Technology Vol. 16

This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author\u27s name. The primary entry includes the coauthors\u27 names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author\u27s name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index

Design and Implementation of High Gain 60 GHz Antennas for Imaging/Detection Systems

Recently, millimeter wave (MMW) imaging detection systems are drawing attention for their relative safety and detection of concealed objects. Such systems use safe non-ionizing radiation and have great potential to be used in several applications such as security scanning and medical screening. Antenna probes, which enhance system performance and increase image resolution contrast, are primarily used in MMW imaging sensors. The unlicensed 60 GHz band is a promising band, due to its wide bandwidth, about 7 GHz (57 - 64 GHz), and lack of cost. However, at 60 GHz the propagation loss is relatively high, creating design challenges for operating this band in MMW screening. A high gain, low profile, affordable, and efficient probe is essential for such applications at 60 GHz. This thesis’s focus is on design and implementation of high gain MMW probes to optimize the performance of detection/imaging systems. First, single-element broadside radiation microstrip antennas and novel probes of endfire tapered slot high efficient antennas are presented. Second, a 57-64 GHz, 1 × 16-element beam steering antenna array with a low-cost piezoelectric transducer controlled phase shifter is presented. Then, a mechanical scanner is designed specifically to test proposed antenna probes utilizing low-power 60 GHz active monostatic transceivers. The results for utilizing proposed 60 GHz probes show success in detecting and identifying concealed weapons and explosives in liquids or plastics. As part of the first research theme, a 60 GHz circular patch-fed high gain dielectric lens antenna is presented, where the prototype’s measured impedance bandwidth reaches 3 GHz and a gain of 20 dB. A low cost, 60 GHz printed Yagi antenna array was designed, optimized, fabricated and tested. New models of the antipodal Fermi tapered slot antenna (AFTSA) with a novel sine corrugated (SC) shape are designed, and their measured results are validated with simulated ones. The AFTSA-SC produces a broadband and high efficiency pattern with the capacity for high directivity for all ISM-band. Another new contribution is a novel dual-polarized design for AFTSA-CS, using a single feed with a pair of linearly polarized antennas aligned orthogonally in a cross-shape. Furthermore, a novel 60 GHz single feed circularly polarized (CP) AFTSA-SC is modeled to radiate in the right-hand circularly polarized antenna (RHCP). A RHCP axial ratio bandwidth of < 3dB is maintained from 59 to 63 GHz. In addition, a high gain, low cost 60 GHz Multi Sin-Corrugations AFTSA loaded with a grooved spherical lens and in the form of three elements to operate as the beam steering antenna is presented. These probes show a return loss reduction and sidelobes and backlobe suppression and are optimized for a 20 dB or higher gain and radiation efficiency of ~90% at 60 GHz. The second research theme is implementing a 1 × 16-element beam steering antenna array with a low-cost piezoelectric transducer (PET) controlled phase shifter. A power divider with a triangular feed which reduces discontinuity from feed lines corners is introduced. A 1 × 16-element array is fabricated using 60 GHz AFTSA-SC antenna elements and showed symmetric E-plane and H-plane radiation patterns. The feed network design is surrounded by electromagnetic band-gap (EBG) structures to reduce surface waves and coupling between feed lines. The design of a circularly polarized 1 × 16-element beam steering phased array with and without EBG structures also investigated. A target detection investigation was carried out utilizing the proposed 60GHz antennas and their detection results are compared to those of V-band standard gain horn (SGH). System setup and signal pre-processing principle are introduced. The multi-corrugated MCAFTSA-SC probe is evaluated with the imaging/detection system for weapons and liquids concealed by clothing, plywood, and plastics. Results show that these items are detectable in clear 2D image resolution. It is believed that the 60 GHz imaging/detection system results using the developed probes show potential of detecting threatening objects through screening of materials and public